As spring gives way to summer, keen gardeners will be as busy as ever. But few will have studied their hobby with any rigour, instead picking up useful skills as children. Why do we value such domestic knowledge less than a formal education?

My first crop of new potatoes is almost ready for lifting. To many listeners this may not seem an event worth recording, let alone celebrating. But one of the drawbacks of being a city-dweller is not having a garden. Instead I have a piece of roof, about the size of a rather large tablecloth, on which I do my best to live out my fantasy of being self-sufficient in home grown vegetables.

As I plant out my seedlings, or encourage my bean plants to wind themselves around their supporting frame, I have the sustaining sense of connecting back to my childhood and my family history, and of taking pleasure in knowing how to care for my own little bit of earth.

LISA JARDINE

People found it disturbing that it so closely resembled a plant which, if consumed, caused a painful death

My potatoes (like my tomatoes) are in large non-matching earthenware containers, on a small terrace among the chimney-pots. When I clamber out to water them, the cool touch and fresh smell of their emerald green foliage fills me with satisfaction, and buoys up my spirits, before I plunge into the Underground for the first of several journeys of the day.

I'd like to be able to tell you that my little roof garden was an urban Eden, but I can't pretend I give it enough attention for it truly to thrive.

Potatoes and tomatoes are something of a horticultural paradox. They belong to the solanaceae family, a distinction they share with the nightshades, including deadly nightshade or belladonna. The tempting, deep blue-black berries of belladonna are fatal if eaten, and yet the similarity between its foliage, flowers and fruits, and those of two of the most widely cultivated vegetables in the world is strikingly close.

Saucy

Today, according to the National Center for Food and Agricultural Policy in Washington, more than 110 million tonnes of tomatoes are produced annually worldwide, with four southern European countries - Greece, Italy, Portugal and Spain - together contributing 15 million tonnes. Two-thirds of all the tomatoes grown are for processing, for everything from tinned tomatoes to ketchup.

Lisa Jardine's urban garden

The potato is now the fourth most important world food crop, after wheat, rice, and maize. In both cases, the cultivation and consumption of an indigenous South American plant, first described by European explorers in the 16th Century, has gradually spread to every continent except Antarctica, and strains have been developed which flourish and produce ample crops in an astonishing variety of climates and types of soil.

The culinary conquest of the world by the potato and the tomato did not, however, happen overnight. In the early days of domestic cultivation of the tomato, people found it strange and disturbing that it so closely resembled a plant which, if consumed, caused a painful death.

Although Europeans - especially Italians - were eating tomatoes raw and including them cooked in recipes by the 18th Century, Americans had to be convinced that they would not be poisoned by them as late as the 19th. A certain Robert Johnson, about whom nothing at all else is known, supposedly achieved a degree of celebrity when he ate a tomato publicly on the steps of the courthouse in Salem, New Jersey in 1820, to prove it would do him no harm.

Chips with everything

The potato was first identified as edible by 16th Century Spanish explorers, who found it under cultivation in Peru, Bolivia, Colombia and Ecuador. They compared the unfamiliar tubers to truffles, and treated them with comparable respect. The earliest specimens, like the tomato, reached Europe in the 16th Century, and were initially used medicinally, in small quantities, as an ingredient in pills, salves and therapeutic potions.

Potatoes grow the world over

The potato quickly spread to Italy, the Low Countries, and the British Isles - the story of the national disaster caused in Ireland by the repeated failure of the potato crop in the 1840s, is, of course, legendary.

The most plausible (though still probably apocryphal) story of the introduction of the potato into Europe attributes its discovery to Sir Francis Drake. In 1585 he led a fleet of some two dozen ships on a piratical expedition to seize and loot the Spanish possessions in the West Indies, bent on bringing back cargo-loads of gold for Queen Elizabeth.

Having plundered, pillaged and burned his way around the islands, he returned to England a year later with no treasure, but with a cargo of booty which included potato tubers and tobacco.

The 16th Century botanist John Gerard produced the first lifelike picture of the potato plant, depicting leaves, flowers and tubers in his 1597 Herball (revised and made even more botanically accurate in the later edition of 1633). The potato plant appears to have held a particular fascination for him, since he is depicted in the Herball's frontispiece illustration, holding a flowering sprig of the potato plant.

Women's work

All of which makes it clear that one of the attractive characteristics of the potato is that it is easy to grow - it thrives almost anywhere, and even the most modestly talented gardener can produce a successful crop.

Delia works her magic on vegetarian food in the 70s

Which in my case is just as well, since as far as I am aware, nobody ever taught me how to garden. When my husband asked me curiously how I knew how to prick out my beetroot seedlings when the first pair of real leaves appeared above the seed leaves, or to earth up my potatoes when the stems reached a certain height, it brought me up short.

Like all the other domestic skills I take for granted, it was my mother who showed me what to do in the garden, just as she taught me how to cast off a piece of knitting neatly, and lay royal icing over marzipan on a cake. None of which I think of as "knowledge".

Knowledge, for me, is learning how to conjugate a Latin verb, or bisect the angle of a triangle using a pair of compasses, or commit to memory the dates of the 17th Century Anglo-Dutch wars. I associate such "knowledge" with formal education, school, university, and the things my father inculcated into me from as early as I can remember.

One of my first conscious memories is of my father showing me how the pieces move on a chessboard. Another is an early birthday present of a set of mathematical instruments, each fitting neatly into its matching slot in a velvet-lined, midnight blue leather case.

I do not think that this pure prejudice in favour of "masculine" education is entirely of my own making. We were simply brought up to take a well-run home for granted.

I remember my paternal grandmother - a formidable woman, with a razor-sharp intellect and an iron will - as permanently exasperated at the absence of any real role for her outside the domestic. She had been heavily involved in London local politics in the 1920s and 30s, but by the time I knew her, her intellectual energies were confined to the housekeeping, where she was only happy when performing a really difficult task with panache.

I have a vivid mental picture of her with a smile of satisfaction on her face as she whipped two egg whites into stiff, brilliant white peaks to make meringues on a flat dinner plate with an ordinary fork, the eggs held on the angled plate by the sheer force of her beating.

How to cook

My generation took cookery and gardening for granted - just things our mothers had shown us how to do. I grew up in a world where the selection of fresh fruit and vegetables in shops and on market stalls closely matched what could be grown in any allotment. So I could easily emulate my mother's dishes, without even thinking.

Today, the fruit and vegetables sections of supermarkets are piled high with unfamiliar produce from every time zone and season. The recipes I learned without noticing are almost irrelevant to an adventurous young cook who wants to prepare exotic dishes involving soy beans, or lemon grass, or callalou. Perhaps that is why TV celebrity chefs - demonstrating the latest fashionable dishes from the global kitchen - are so extraordinarily popular.

The tomato and potato were once strange foodstuffs, offering opportunities for an inventive new cuisine. Like them, all the exotic vegetables I just named will happily grow here in Britain.

So now that I have conceded that gardening is something that requires to be learned, I am going to expand my horticultural horizons - resist my urge to succumb to the nostalgia of what I already know. Next season I'm planting chillies, okra and pak choi in my multi-coloured pots among the chimneys.

Below is a selection of your comments.

I rather suspect the current generation will only have learned how to shop at Tescos. Gardening skills will either be lost or have to be learned from a book...Nick, Sheffield

How true. My old school would have been horrified if anyone had called gardening "knowledge". Yet, if I think back on what has been important to me, or has enriched me during my life, I have to say that very little of my school curriculum falls into that category. Perhaps though I wasn't the kind of student my school wanted or valued. I became a scientist.Nick Morton, Camborne, Cornwall

Hoorah! It's good to see an article on this. I almost have to hide my enthusiasm for cultiavting my own veg (potatoes, tomatoes, bean, radishes, parsnips, onions, sweetcorn, cucumbers etc. etc.) from my work collegues as it seems to have as much of a social stigma as stamp collecting or train spotting. I knew nothing about gardening when I started, I was just curious to see if I could grow anything. It feels quite special to enjoy the fruits (and vegetables) of ones labour.Dan, London

I knew nothing about gardening except what a pansy was and what were classed as weeds, according to my dad. I'm now 27, have worked in a plant nursery for the past 5 years and i'm amazed at just how much i know now, about how those 'weeds' were actually nice plants and at just how easy it is for us all to grow our own little herb/veggie garden. Imagine 25% of a city growing and sharing their own produce....organic bliss!Stuart, Kingston Canada

Your first crop of new potatoes is a milestone in your gardening life, its like finding lumps of gold, have had a allotment for 4 years the taste and quality of all that you grow is far better, than you can buy.louis fernandez, cardiff s glam

"The potato was first identified as edible by 16th Century Spanish explorers, who found it under cultivation in Peru, Bolivia, Colombia and Ecuador." So why were the locals cultivating the potato? What did they use it for? Or had they, perhaps, identified it as edible long before a white, European explorer came along? So that wouldn't count.Adrian Jones, Edgware

Welcome to the wonderful world of Grow Your Own! For many years we too did potatoes tomatoes beans and the like but recently we have discovered the extra fun that can be had from growing exotic things, varieties and species that you simply can not buy in the shops. The result is a fabulous adventure in taste!Jenny Day, Saltash Uk

Seven years ago, I used to live in a one room flat with my then husband. I had some window boxes to grow herbs and some flowers in. My husband laughed at me, claiming the seeds I planted would never grow. The when they had grown to bushy, healthy plants, he refused to eat them because they hadn't been bought in plasic wrapping from a supermarket. He considered them 'dirty' so therefore inedible. I think this indicated part of the current prejudice for home grown food. I think because people see the dirt that the food is grown in, they believe it's not safe to eat. Now I have a large enough garden to grow a good crop of veg and a partner who is as keen to get his hands in the dirt as me!Heather, Wolverhampton

Although allotment availability is obviously unequally distributed in the country ( around a quarter of allotments in my area are unused whilst my sister-in-law says there is a 4 year waiting list in Camden), it is greatly rewarding to put your dinner on the table that you have grown (at least the fruit and veg) yourself. It's also good to show my two year old that food doesn't just come from Tesco!Jamie Pringle, Stoke-on-Trent

I have also started "pot gardening", and I am learning all the time, mainly from my mistakes. I find it great fun and rather soothing! This year I have a lot of Chinese Cabbage. My wife is Korean and I am hoping that my mother-in-law, on her next visit, will be able to turn this crop into some of the finest "Kimche" that any Korean would love to devour!Roland Brade, Deal, Kent